Hydrolysis of amides. VI. Dilute acid hydrolysis of N-alkyl substituted acetamides

1972 ◽  
Vol 25 (2) ◽  
pp. 303 ◽  
Author(s):  
PD Bolton ◽  
J Ellis ◽  
RD Frier ◽  
PC Nancarrow
Keyword(s):  
Free Energy ◽  
Acid Hydrolysis ◽  
Rate Constants ◽  
Rate Data ◽  
Linear Free Energy Relationships ◽  
Dilute Acid ◽  
Dilute Acid Hydrolysis ◽  
Linear Free Energy ◽  
Energy Relationships ◽  
Hydrolysis Of

Enthalpies and entropies of activation have been derived from rate constants measured over a range of temperature for the dilute acid hydrolysis of N-methyl- acetamide, N-ethylacetamide, N-n-propylacetamide, N-isopropylacetamide, N-n-butylacetamide, N-s-butylacetamide, N-isobutylacetamide, N-isopentyl-acetamide, N-n-hexylacetamide, N-cyclohexylacetamide, and N-benzylacetamide. An analysis of the rate data in terms of several Taft-type linear free energy relationships indicates that the change in steric environment which a substituent experiences when it is moved from the acyl part to the alkyl part of an amide is quantitatively similar to the change in steric environment experienced by the same substituent in moving from the acyl to the alkyl portion of an ester. Evidence is also presented that the change in six-number makes the greatest contribution to the change in steric environment.

Hydrolysis of amides. IV. Dilute acid hydrolysis of amides of the type R2CH-CONH2 and R3C-CONH2

1971 ◽  
Vol 24 (3) ◽  
pp. 471 ◽  
Author(s):  
PD Bolton ◽  
GL Jackson
Keyword(s):  
Free Energy ◽  
Hydrogen Bonding ◽  
Acid Hydrolysis ◽  
Rate Constants ◽  
Hydrolysis Rate ◽  
Dilute Acid ◽  
Dilute Acid Hydrolysis ◽  
Reasonable Explanation ◽  
Hydrolysis Of

Enthalpies and entropies of activation have been derived from rate constants measured over a range of temperature for the dilute acid hydrolysis of isobutyramide, diethylacetamide, α-methylbutyramide, cyclohexaneoarboxamide, cyclopentane-carboxamide, and trimethylacetamide. ��� These data, in combination with data for other amides produced earlier, show the hydrolysis rate constants to be dominated by steric influences but with a perturbing effect which is proportional to the number of α-hydrogens present in the substituent. The "α-hydrogen bonding" concept of hyperconjugation appears to offer a reasonable explanation of these perturbations. ��� Controlled steric changes are shown to be non-additive for this reaction and to exert their influence primarily through the enthalpy component of the observed free energy changes.

Hydrolysis of amides. III. Dilute acid hydrolysis of amides of the type R-CH2-CONH2

1969 ◽  
Vol 22 (3) ◽  
pp. 527 ◽  
Author(s):  
PD Bolton ◽  
GL Jackson
Keyword(s):  
Acid Hydrolysis ◽  
Linear Dependence ◽  
Rate Constants ◽  
Dilute Acid ◽  
Dilute Acid Hydrolysis ◽  
Hydrolysis Of

Rate constants over a range of temperature, enthalpies of activation, and entropies of activation are reported for the dilute acid hydrolysis of n-valeramide, isovaleramide, 3,3-dimethylbutanamide, phenylacetamide, cyclohexylacetamide, methoxyacetamide, bromoacetamide, and chloroacetamide. ��� The rate constants of the first six amides together with those of two other alkyl-substituted acetamides taken from a previous paper are almost perfectly correlated by the Taft linear steric energy relationship. The enthalpies of activation, also, show a linear dependence on the steric parameter, Es. The results obtained for the halogeno amides indicate that the acid hydrolysis of amides may show a slight sensitivity to polar effects.

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